1. Field of the Invention
The present invention generally relates to a driving circuit of a display apparatus, more particularly, to a method and apparatus to generate control signals for a display-panel driver.
2. Description of Related Art
In the system structure of a conventional thin film transistor liquid crystal module, in order to attain the requirement of higher image quality or the goal of having a more efficient and more flexible system design applications, additional control lines between the controller and the source/gate driver are provided and additional chip pads corresponding to the source/gate driver are required to implement new driving control functions and function selection controls. This leads to inflexibility of function expansion and lowering of cost-effectiveness.
FIG. 1 is a diagram of a conventional thin film transistor liquid crystal display module. As shown in FIG. 1, the thin film transistor liquid crystal module 100 includes a liquid crystal panel 102, an X-PCB 104, a Y-PCB 106, a controller 108, source drivers SD1˜SD8, gate drivers GD1˜GD3, source driver films 110 and gate driver films 112, for example. Digital display data are processed by the controller and converted to a suitable data format and control signals. Together with clock signals CLK and GCLK used as reference for synchronous data reception, the data and control signals are sequentially transmitted to the source drivers SD1˜SD8 and the gate drivers GD1˜GD3.
FIG. 2 is a timing diagram of the control signals of a conventional source driver. As shown in FIG. 2, in order to save more power of the system, a conventional serial connection structure together with control signals serving as the control for enabling the driver on or off are deployed. For the source driver, the most basic control signals, aside from the start pulse SPI/SPO, include the latch signal STB and the polarity signal POL. However, in order to attain better image quality, newer driving control functions are continuously developed. To control these newly added functions, additional control lines between the controller and the source drivers are normally required. For example, the widely adopted Horizontal 2Dot Inversion function requires two additional control lines, namely, H-2DOT and POLC. In addition, in order to have more efficient and more flexible system design applications, the source driver also includes a number of function selection controls, for example, multi-channel selection, low power mode selection and charge sharing selection so as to provide the development requirements for different system applications. These added function selection controls require additional chip pads to implement the selection control.
FIG. 3 is a block diagram illustrating the functions of a conventional source driver. As shown in FIG. 3, a conventional source driver 300 includes a shift register 302, a data latch 304, a level shifter 306, a Digital-to-Analog Converter (DAC) 308, an output circuit 310, a clock input comparator 312, a data receiver 314, and a data register 316. Because the source driver 300 has to respond to different functions, input terminals are set up to receive a number of input signals, for example, HDOT, POLC, POL, . . . and so on, while corresponding control signals are output to drive the pixel for displaying data.
In other words, the input terminals of a conventional driver need to have chip pads. Therefore, a larger chip size is required and production cost is likely to increase. With the trend for market expansion and cost reduction, how to increase the number of control function of the product and simultaneously minimize the number of control pads for function selection is at the top of the product development goal.